Photoconductive time delay device



Aug- 2, 1966 R. J MOLDOVAN 3,264,478

PHOTOCONDUCTIVE TIME DELAY DEVICE Filed April 18, 1965 INVENTOR, RICHARD J. MOLDOVAN.

W fi fl yw ATTORNEY United States Patent 3,264,478 PHOTOCONDUCTIV E TIME DELAY DEVICE Richard J. Moldovan, 4201 Domenico Court, Bridgeton, M0.

Filed Apr. 18, 1963, Ser. No. 273,940 6 Claims. (Cl. 250---206) The invention relates to photoconductive control de vices and consists particularly in a photoconductive control device with time delay means.

It is a main object of the invention to provide a photoconductive control device embodying selective time delay means whereby the load can be energized a selected time after exposure of the photoconductive cell to light.

I achieve this object by providing a photoconductive cell in the circuit of an electric motor, and driving a rotatable switch activating arm by the motor, the arm normally being spring biased against a stop positioned relative to the arc of rotation of the arm in accordance with the desired time delay, so that the rotary travel time of the arm, from the stop until it closes the switch, equals the desired time delay.

In the schematic representation of my invention shown in the drawing, an electric motor 1 is connected to an alternating current source 2 of commercial voltage, and for controlling the operation of the motor in accordance with light conditions, the motor circuit includes a photoconductive cell 3 in series with the motor. Motor shaft 4 is connected by gears 5 and 7 to a hollow shaft 9 on which is fixedly mounted switch operating arm 11.

Timer shaft 13 is coaxial with and is journaled within hollow shaft 9 and mounts stop arm 15 formed with a stop bar 17 extending parallel to shaft 13 and adapted to engage switch operating arm 11 and limit clockwise movement of the latter. Operating arm 11 is normally biased in a clockwise direction and yieldably held against stop bar 17 by resilient means such as torsion spring 19, anchored at one end to bar 17, and secured at its other end to arm 11, arm 11 being rotatable counterclockwise away from engagement with stop bar 17 by motor 1 when the latter is energized. Shaft 13 also fixedly mounts a manual adjusting knob 21, overlying a stationary scale 23, graduated in units of time, so that, by rotation of knob 21 until its index mark registers with the desired time lag on the dial, stop bar 17 will be correspondingly rotated, and the initial position of operating arm 11 similarly varied.

The outer end of operating arm 11 is convexly rounded as at 25, for engagement with a similar but concave surface 27 on lever 29, which is pivoted intermediate its ends on stationary shaft 31. The lower end of lever 29 is rounded for sliding engagement with the upper surface of switch operating bar 33. The latter is fulcrumed at one end on a fixed axis 35 and intermediate its fulcrum and its point of engagement with lever 29, its lower surface engages outwardly biased plunger 37 of snap action switch 39. Switch 39 is connected in series with a source of power 41 and load 43, so as to energize the load when closed.

With this arrangement, when the resistance of photoconductive cell 3 is reduced to a predetermined value by its exposure to light of predetermined intensity, motor 1 begins to operate, causing counterclockwise rotation of operating arm 11 away from stop bar 17, in opposition to spring 19. While rotating, arm 11 engages surface 27 of lever 29, producing clockwise rotation of the latter, and downward movement of bar 33 to its broken line position shown in the drawing, until switch plunger 37 is fully depressed, thus preventing further downward movement of bar 33 from the broken line position, further clockwise movement of lever 29 as a result of its engagement with the upwardly extending left hand end of bar 33, and

through engagement of surfaces 27 and 25, any further counterclockwise movement of arm 11. This stalls motor 1, but as long as it is energized, it continues to produce torque to hold arm 11 in its final position and thus maintain switch 39 closed. When the light is extinguished or reduced below a predetermined intensity, with consequent increase in the resistance of cell 3 above a predetermined value, the torque of motor 1 becomes less than that of spring 19, so that the latter produces clockwise rotation of arm 11 away from lever 29, freeing lever 29, and permitting microswitch plunger 37 to rise to its normal height, thereby opening the switch.

Operation of the device is as follows: Manual adjusting knob is rotated until its index registers with the desired time delay on dial 23, thereby rotating shaft 13 and stop 17 so that angular distance, measured counterclockwise from stop 17, between stop 17 and surface 27 of lever 29, is proportional to the desired time delay. With photoconductive cell 3 unexposed to light and its resistance relatively high, motor 1 produces insufficient torque to overcome the torque of spring 19, which accordingly biases arm 11 toward and against stop 17.

When light of predetermined intensity strikes cell 3, its resistance is lowered sufficiently that motor 1 develops sufficient torque to overcome that of spring 19, and arm 11 is rotated counterclockwise into engagement with lever 29, causing the latter to rotate, until the latter, through bar 33 fully depresses switch plunger 37, after which further clockwise movement of lever 29 is prevented. This prevents further counterclockwise movement of arm 11 and causes the motor to stall, but the motor, though stalled, continues to develop torque as long as the light of sufficient intensity strikes cell 3. When the light is reduced below the predetermined intensity, or removed, the resistance in the cell increases, with a proportionate drop in the motor torque below the value of the spring torque, permitting the spring to rotate arm 11 clockwise away from lever 29, thereby permitting switch plunger 37 to rise and open the circuit through load 43. Spring 19 continues to rotate arm 11 until the latter engages stop 17 after which the device is ready for another cycle.

It will be understood, of course, that the device may incorporate a normally closed switch instead of the normally open switch 39 described above. In the event a normally closed switch is used, the light-responsive operation of the device will open the load circuit instead of close it as in the above-described operation.

The details of the device disclosed herein may be varied substantially without departing from the spirit of the invention and the exclusive use of those modifications coming within the scope of the appended claims is contemplated.

What is claimed is:

1. A photoconductive control device comprising an electrical circuit including a source of power, a motor, and a photoconductive cell connected in series with said motor, said cell being adapted to vary resistance in said circuit in accordance with changes in light intensity, an arm drivably connected to said motor and rotatable thereby in one direction only, a stop means adapted to limit rotation of said arm in a direction opposite to that in which said motor is adapted to rotate said arm, resilient means connected to said arm and biasing the same toward engagement with said stop means, a load circuit including an electrical switch, said motor developing a torque greater than that of said resilient means when the resistance of said motor circuit is reduced to a predetermined value by said cell, a lever angularly spaced about the rotational axis of said arm from said stop means and adapted to engage said arm and be rotated thereby when the latter is rotated away from said stop means by said motor, said switch having an element operatively connected to said lever for movement from one position to another when said lever is rotated.

2. A photoconductive control device according to claim 1 in which said stop means is variably positionable about the axis of rotation of said arm whereby to vary the angular distance between said stop means and said switchoperating means and the time required for rotation of said arm therebetween.

3. A photoconductive control device according to claim 2 including manual means for positioning said stop means.

4. A photoconductive control device according to claim 3, in which there is a scale in registry with said manual means and calibrated in units of time in accordance with the motor-driven speed of said arm.

5. A photoconductive control device according to claim 1 in which the engageable portion of said lever and said arm are respectively mating concave and convex surfaces.

References Cited by the Examiner UNITED STATES PATENTS 2,123,470 7/1938 Lamb 250206 X 2,292,911 8/ 1942 Timmons 20038 2,946,902 7/1960 Hagen 200-38 RALPH G. NILSON, Primary Examiner.

WALTER STOLWEIN, Examiner. 

1. A PHOTOCONDUCTIVE CONTROL DEVICE COMPRISING AN ELECTRICAL CIRCUIT INCLUDING A SOURCE OF POWER, A MOTOR, AND A PHOTOCONDUCTIVE CELL CONNECTED IN SERIES WITH SAID MOTOR, SAID CELL BEING ADAPTED TO VARY RESISTANCE IN SAID CIRCUIT IN ACCORDANCE WITH CHANGES IN LIGHT INTENSITY, AN ARM DRIVABLY CONNECTED TO SAID MOTOR AND ROTATABLE THEREBY IN ONE DIRECTION ONLY, A STOP MEANS ADAPTED TO LIMIT ROTATION OF SAID ARM IN A DIRECTION OPPOSITE TO THAT IN WHICH SAID MOTOR IS ADAPTED TO ROTATE SAID ARM, RESILIENT MEANS CONNECTED TO SAID ARM AND BIASING THE SAME TOWARD ENGAGED WITH SAID STOP MEANS, A LOAD CIRCUIT INCLUDING AN ELECTRICAL SWITCH, SAID MOTOR DEVELOPING A TORQUE GREATER THAN THAT OF SAID RESILIENT MEANS WHEN THE RESISTANCE OF SAID MOTOR CIRCUIT IS REDUCED TO A PREDETERMINED VALUE BY SAID CELL, A LEVER ANGULARLY SPACED ABOUT THE ROTATIONAL AXIS OF SAID ARM FROM SAID STOP MEANS AND ADAPTED TO ENGAGE SAID ARM AND BE ROTATED THEREBY WHEN THE LATTER IS ROTATED AWAY FROM SAID STOP MEANS BY SAID MOTOR, SAID SWITCH HAVING AN ELEMENT OPERATIVELY CONNECTED TO SAID LEVER FOR MOVEMENT FROM ONE POSITION TO ANOTHER WHEN SAID LEVER IS ROTATED. 